the easiest way would be to add an action for the clock hand to:
"Set Angle Towards Position" and use Touch.X and Touch.Y as the position.
as long as the origin of the hand is the base of the hand, and the hand points to the right (zero degrees) initially, it will work...
however, if you want the hand to ONLY point exactly to a number, then make each of the numbers a separate sprite, and put them all in a family. Then when you touch any family member, set the angle of the hand to the number's position.